I know you're just being dopey, particularly since you excluded bats which are indeed flying mammals. But there is an answer, none the less. Flying is very expensive. It burns a lot of energy, and requires that you sacrifice things like heavier, stronger bones.

they evolved to above-ground, large, diurnal. no Big changesto fly they'd need smaller bones, different fur, different lungs and muscles and ... imagine flying while preggers. Bats (i suspect) manage because they stayed nocturnal and underground. (Whales only needed to lose the fur and legs and get better lungs ..and the Ocean was a wide-open niche for a big-brain predator)

And why could mammals not evolve light bones? And high-energy muscles? What law of evolution precludes this?

See JT's answer for most of this. Also note that on more than one occasion, birds have opted for only occasional flight (turkeys, chickens) or no flight at all (kiwis, ostriches) because it was cheaper.

curious .... was that a 'choice' for the Chickens ..or part of their domestication?

I've done zero research on this, but I expect chickens were probably near-flightless before domestication. Because I doubt they'd have been domesticated if they did fly.

Choice of course is a very misleading word when talking about evolution. It's chance and selection pressure, but it's easy shorthand for saying "ur-chickens which were bigger and less able to fly reproduced more often than ur-chickens that were smaller and flew more."

and Kiwis lived where there were no predators.

Right, flight is mostly about avoiding being eaten. No one eating you, no reason to keep flying.

During the breeding season, the male birds announce their presence with the well known "cock-a-doodle-doo" call. This serves both to attract potential mates and to make other male birds in the area aware of the risk of fighting a breeding competitor. The lower leg just behind and above the foot has a long spur for just this purpose. ...

Flight in these birds is almost purely confined to reaching their roosting areas at sunset in trees or any other high and relatively safe places free from ground predators, and for escape from immediate danger through the day.

And why could mammals not evolve light bones? And high-energy muscles? What law of evolution precludes this?

No law prevents it, as should be obvious by the fact that some animals (including bats, which are mammals) DID evolve in exactly that way.

The flaw in your thinking is your idea that every feature which is helpful in some way should be available universally. In reality, every species has strengths and weaknesses, and the effect of evolution is that it sort of naturally "chooses" an area of specialization.

It's sort of like if you asked your dentist why he doesn't know how to do open heart surgery. You might say "Why couldn't you learn open heart surgery? Don't you think that would be a valuable skill for you to have?" No one would say that it's not a valuable skill, but based on his personal circumstances and choices, he's a dentist. He has a career in that. It wouldn't HURT to know about open heart surgery as well, but the payoff would not be good enough to justify the extra time and effort that goes into learning it.

Similarly, it's not bad for an animal to be able to fly. But it wouldn't be very useful for, say, a grizzly bear to evolve into a flying animal. Because moving in a direction that makes flight feasible would require certain features to change that would make it less good at being a grizzly bear.

Similarly, it's not bad for an animal to be able to fly. But it wouldn't be very useful for, say, a grizzly bear to evolve into a flying animal. Because moving in a direction that makes flight feasible would require certain features to change that would make it less good at being a grizzly bear.

Yep. I've read that it's likely that feathers evolved as a fur-substitute, from scales, long before they became useful as flight enablers and control surfaces. Some proto-birds were almost certainly already small, light creatures before taking wing. Perhaps they were gliders first, or running about and swatting at flying insect prey with feathered forearms? It's an interesting question, and I always enjoy hearing about new fossils that shed light on the early history of birds.

But they didn't make the leap from walking to flying in one easy step, and more than a grizzly could become a flyer without eventually becoming a not-grizzly.

I'm just a-thinkin' that flying with a noggin that makes wheels and plays with fire would be as difficult as flying preggers.

So we gots the noggin instead of the wings.

as Gus sez .... really big noggins only come near the end of the Age of Mammals (just prior to Age of Cucarachas)

and ,i think, "bird brain" is a myth... bird brains are small because birds are small .. from what i've read -- 'higher' Birds (Parrots and Crows) have higher brain-to-body mass ratio than average Mammal (though well below 'higher' Mammals). And though the bit of brain anatomy we use to invent shotguns is small in all birds, another bit of anatomy is larger and thought to be used by the Birds for their 'reasoning' and problem solving...

i've probably told the story about the local Jay who out-smarted me ... so

AM touched on the story of the Ravens --

we pull into the parking lot of a scenic vista viewpoint ... i get out of the car and a Raven waddles over to me. Maybe 'he' waddles over to everyone; maybe i have the face of someone who has peanuts and will share... whichever, i throw 'him' a peanut. he takes it and starts trying to hide it under some debris. Another Raven flies over and coos at him, as if to say, "What-cha DOO-in honey?" He croaks 'trying to hide this peanut ..now you're here, i'll have to eat it." 'She' tries to steal it; he croaks, 'oy. go see the guy in the funny hat!'. She does; i throw her a peanut... then another & another --and i'm out of peanuts (one of the few states that truly troubles me).

we drive up the road a bit, past a big sign, "Do NOT feed the wild animals". i say, "heh. looks like they know to hang out far from the sign so they can beg for snacks"

driving back down, past the sign, they're standing under the sign...AM says, "or they interpret the sign differently, 'WE're not wild animals. We're Ravens --highest life form on the planet. & not bloody likely WE will feed any of these wild tourist-monkeys'"

The flaw in your thinking is your idea that every feature which is helpful in some way should be available universally.

Right, and when you pair "every feature should have evolved by now!" with the "cool new features can't evolve; they're too complicated!", you see that these two arguments against evolution actually conflict with one another.

In reality, every species has strengths and weaknesses, and the effect of evolution is that it sort of naturally "chooses" an area of specialization.

We're not talking about a species evolving here, we're talking about a huge major taxononmic group - mammals - of which we know a couple offshoots did evolve flight ability (bats and if you want to count flying squirrels). In other words, proof-of-concept is already there. Why did the trait not go further?

it wouldn't be very useful for, say, a grizzly bear to evolve into a flying animal. Because moving in a direction that makes flight feasible would require certain features to change that would make it less good at being a grizzly bear.

Uh... I don't know where to start with that one. Maybe you were joking.

We're not talking about a species evolving here, we're talking about a huge major taxononmic group - mammals - of which we know a couple offshoots did evolve flight ability (bats and if you want to count flying squirrels). In other words, proof-of-concept is already there. Why did the trait not go further?

Why should it? You seem to be starting from the premise that "flying" is ipso-facto a better condition than "not flying" for a species. A species don't care if it's flying, swimming, crawling, or rooted in place. If there's an empty niche to be exploited, some species or set of them will evolve over time to exploit it. But that doesn't mean they all will.

Why should it? You seem to be starting from the premise that "flying" is ipso-facto a better condition than "not flying" for a species. A species don't care if it's flying, swimming, crawling, or rooted in place.

We're not talking about a species evolving here, we're talking about a huge major taxononmic group - mammals - of which we know a couple offshoots did evolve flight ability (bats and if you want to count flying squirrels). In other words, proof-of-concept is already there. Why did the trait not go further?

Why should it? You seem to be starting from the premise that "flying" is ipso-facto a better condition than "not flying" for a species. A species don't care if it's flying, swimming, crawling, or rooted in place. If there's an empty niche to be exploited, some species or set of them will evolve over time to exploit it. But that doesn't mean they all will.

Also, if all creatures were able to fly they would need approximately the same kinds of food which would, logically, become scarce. With diversity, the various species are able to take advantage of various foodstuffs -- with less competition for them than they would experience if all creatures were after the same things.

But you're assuming those are all the only, or best ways to be successful as a species. As has already been stated here, flying doesn't come for free. I'm not sure why you're ignoring that, unless you have some agenda you're attempting to be subtle about?

Flying requires a lot of calories. Many species do quite well crawling slowly along.

It's difficult to be very large when you fly, and in some niches being large is the way to be successful. It allows to exploit sources of food (like, smaller creatures) that being smaller would disallow.

And droughts, floods, and other infrequent catastrophes cannot be evolved for.

Unless the "floods" are things like tidal zones, in which case you succeed (or not) by evolving to exploit that ecology, like being able to persist buried under the mud until the next "flood", or by being able to hunt for those mud-dwellers along the edge when the "flood" recedes.

Or unless the "droughts" are deserts, in which case you evolve by being really good at conserving water, or being strictly nocturnal, or learning to drink dew deposited on your own body in the morning.

And in the long run, what matters is not what happens to individuals. Who cares if a few thousand caribou are drowned in a flood when a glacial dam bursts? Sucks to be them. But as long as the species is spread far enough, it survives, and that's all that matters.

I've done zero research on this, but I expect chickens were probably near-flightless before domestication. Because I doubt they'd have been domesticated if they did fly.

Chickens can fly, but usually don't opt to. It takes a lot of energy just for a short flight. When raising chickens on the farm, sometimes the feisty ones kept flying out of the pen. We'd clip the feathers on one side. This caused them to fly in a circle, unable to get over the fence.

I suspect that certain breeds of chickens are more capable of flight than others.

you're assuming those are all the only, or best ways to be successful as a species.

No, I did not ask why all mammals dont start flying, I only asked why almost none of them do.

As has already been stated here, flying doesn't come for free. I'm not sure why you're ignoring that

Who said evolution was free? There's a lot of pain involved for the individuals. Most are naturally selected against. Only the strong survive. But evolution happens because there are gains to be had. I listed a few of them.

droughts, floods, and other infrequent catastrophes cannot be evolved for.

OK I guess all the migrating wildebeest on the Serengeti, and the geese and storks and thousands of other migratory birds just have wanderlust.

unless you have some agenda you're attempting to be subtle about?

My agenda is to learn, or if the answer is 'nobody knows' then that is fine too. That's my conclusion so far from the guesswork proffered on this thread. That's fine, it would be OK for atheists to admit they dont know something; I dont have the answer either. In fact thats why I asked the question. Rational beings ought to admit they dont know when they dont know, rather than make stuff up.

Its the religious who seem compelled to invent fantasies when they really haven't got a clue.

"Oh, the humanity! The turkeys are hitting the ground like sacks of wet cement!"

Based On RealityOddly enough, this famous WKRP episode was loosely based on a real event! Back in 1946 (some sources say 1945), Yellville, Arkansas inaugurated the "Turkey Trot Festival" which included a wild turkey calling contest, a turkey target shoot, a Miss Drumsticks Pageant and oh yeah: a live turkey release from the roof of the courthouse. After a few years, someone thought it might be fun to actually toss the poor gobblers out of a low-flying airplane for the event. This repeated for a number of years until 1989 when a national animal-rights protest cast the event in a bad light and the "National Enquirer" splashed a photo of the event across the nation forcing promoters to abandon the turkey drop.http://radio.about.com/library/weekly/blwkrpturkey.htm

No, I did not ask why all mammals dont start flying, I only asked why almost none of them do.

I don't know, but I can guess it's probably because it's a highly specialized skill. As a mammal, you likely need to start with a certain set of traits that lend themselves to it, I'd guess.

Good vision (or its sonar equivalent), almost certainly.

Small body size, probably.

High metabolism, probably.

Sloths and grizzly bears are not well-positioned to evolve into fliers.

Why pick flight, by the way? Why not ask, Why don't more mammals become tunnelers? There would seem to be many benefits of that niche too.

Who said evolution was free? There's a lot of pain involved for the individuals. Most are naturally selected against. Only the strong survive. But evolution happens because there are gains to be had. I listed a few of them.

Evolution doesn't care what direction it goes in though. The niche of "flier" is already well-exploited.

OK I guess all the migrating wildebeest on the Serengeti, and the geese and storks and thousands of other migratory birds just have wanderlust.

Fair enough, point taken. Though I suspect the birds are migrating more to find more abundant sources of food, and safer nesting grounds, than for drought?

My agenda is to learn, or if the answer is 'nobody knows' then that is fine too. That's my conclusion so far from the guesswork proffered on this thread. That's fine, it would be OK for atheists to admit they dont know something; I dont have the answer either. In fact thats why I asked the question. Rational beings ought to admit they dont know when they dont know, rather than make stuff up.

Sheesh, you sure are prickly. This is the "Atheist Fools" group, not the "Evolutionary Specialists" group.

In any case, I thought it was a given that none of us know for a certainty, in the absolute proof sense, the answers to questions like this.

No, I did not ask why all mammals dont start flying, I only asked why almost none of them do.

The answer is in your question. Focus on the word "almost". If "almost" none do, then some do.

Why don't most fish walk? Well, some do, because they evolved protolegs which can carry them across land. But this is a largely unnecessary trait, so most do not.

When "most" do, they are not "fishes" anymore ;)

droughts, floods, and other infrequent catastrophes cannot be evolved for.

OK I guess all the migrating wildebeest on the Serengeti, and the geese and storks and thousands of other migratory birds just have wanderlust.

Actually all of those things can be evolved for, except the animals may not know it at the time. There are many "improvements" which are improvements only in hindsight, because they provide an advantage which gives the species a better chance at survival later. If I evolve a better way to store water against drought, so long as that does not disadvantage me in some way, I may carry that "unseen" advantage for generations, even eons, until a drought hits. Then those without that gene die, and I survive. Ergo: evolution.

Evolution happens in very strange, and as yet not well understood ways. One example, linked somewhere on this board (I can't seem to find it) is that when wolves were bred for a particular coat color - other things happened which the researchers could not have, and did not predict. I seem to recall that when their coats went white, they also became significantly more vocal. Now "white coat" could have been "selected" in northern climes where such camouflage would have been helpful against snow, but perhaps "more vocal" was irrelevant. Maybe it was even a bad thing. Unless the snow camouflage was so good that when they got in trouble, Mama wolf couldn't find her kids unless they were loud enough to follow, ergo: a niche of success.

It would be swell if we had a time lapse recording of all animal history and could see which things survived - and why - and what adaptations were made - and when - and in response to what, but we don't. Just as we don't have a film of how the thousands of layers of silt and sand got deposited in Arizona and later became the Grand Canyon. But we can form some opinions and make some conclusions, even though we can't prove them precisely, absolutely, with perfect 100% confidence.

So it is with "why don't mammals fly?" Well, they do, a few of them. And if it were none of them, so what? Why aren't there chartreuse oranges or 30 foot tall mosquitos? Those are at least as relevant questions, in my view.

So it is with "why don't mammals fly?" Well, they do, a few of them. And if it were none of them, so what? Why aren't there chartreuse oranges or 30 foot tall mosquitos? Those are at least as relevant questions, in my view.

Exactly.. you might say the OP begs the question by purposefully selecting a group of animals that didn't diversify in a direction. You might as easily say "Why don't some birds run instead of flying?" or "Why don't mammals swim?" or so on (and the answer is - they do!). It makes more sense to say that all this diversity "proves" evolution than to say an a little lack of diversity disproves evolution.

I'm sure you know the reason for the latter: the square cubed law. Exoskeletons and open circulatory systems won't support 30 foot tall bodies.

Even more interesting is the question of how Meganeura Monyi managed to survive. Those dragonflies, at 18 inches long and with a wingspan of 2.5 feet, are bigger than theory says insects should be. They just shouldn't be able to oxygenate their tissues properly with a tracheal breathing system.

Even more interesting is the question of how Meganeura Monyi managed to survive. Those dragonflies, at 18 inches long and with a wingspan of 2.5 feet, are bigger than theory says insects should be. They just shouldn't be able to oxygenate their tissues properly with a tracheal breathing system.

I thought that the reason such huge insects evolved was because millions of years ago, the oxygen content of the atmosphere was much higher than it is now (sorry, can't quote specifics). Or is M. Monyi too big even accounting for that?

Evolution happens in very strange, and as yet not well understood ways. One example, linked somewhere on this board (I can't seem to find it) is that when wolves were bred for a particular coat color - other things happened which the researchers could not have, and did not predict. I seem to recall that when their coats went white, they also became significantly more vocal. Now "white coat" could have been "selected" in northern climes where such camouflage would have been helpful against snow, but perhaps "more vocal" was irrelevant. Maybe it was even a bad thing. Unless the snow camouflage was so good that when they got in trouble, Mama wolf couldn't find her kids unless they were loud enough to follow, ergo: a niche of success.

I watched something a while back that was similar to this. It was about a Russian biologist who was sent to Siberia. There, he began breeding foxes. He was asked by some fellow exiles if he could breed a more domestic fox that they could keep as pets. So, he began selectively breeding the most docile foxes. And something strange happened; their coats began to change colors and their ears began taking different shapes.

If I recall correctly, the now accepted explanation for this is that certain genetic traits lie in pathways in conjunction with other traits. The genes that affect temperament lie in the same genetic pathway as genes for coat color, ear and tail shape and size, etc.

This was of great interest to biologists trying to unravel the evolution of domestic dogs from their wild counterparts, and why domestic dogs (and cats) exhibit such a greater variety of shapes and sizes than wild ones. The theory they came up with was that wolves (or perhaps coyotes or some other canis) began feeding on food scraps on the outskirts of human encampments. Those animals who were less fearful of humans (and less threatening to them) were naturally selected, and gradually evolved into a more domestic species. The distinct physical traits of many domestic dogs (waggy tails, floppy ears, spotted or variegated coats, etc) was an evolutionary byproduct of temperament selection.

So, one of the challenges of evolutionary science is to separate those traits that were specifically selected for from those that may simply be byproducts of selection for other traits.

Just thought that was an interesting story, and finally got an excuse to relate it ;)

Chickens can fly, but usually don't opt to. It takes a lot of energy just for a short flight. When raising chickens on the farm, sometimes the feisty ones kept flying out of the pen. We'd clip the feathers on one side. This caused them to fly in a circle, unable to get over the fence.

Chicken Run, a movie about escape from the pen, is one of my favorites.

Even more interesting is the question of how Meganeura Monyi managed to survive. Those dragonflies, at 18 inches long and with a wingspan of 2.5 feet, are bigger than theory says insects should be. They just shouldn't be able to oxygenate their tissues properly with a tracheal breathing system.

- Gus

I like the one that asks how there can be girafes? Why don't they burst a blood vessel in their head when they put their head down? How can their heart pump blood all the way up tp their head? A single action pump can't do that.

And why could mammals not evolve light bones? And high-energy muscles? What law of evolution precludes this?

None, bats fly.

But besides that, a primary advantage of flying is the ability to elude predators. In places were there are no or few predators, birds lost the ability to fly. Examples include ostriches in Australia, kiwis in New Zealand and penguins in the Antarctic. Evolution in action, baby.

I watched something a while back that was similar to this. It was about a Russian biologist who was sent to Siberia. There, he began breeding foxes. He was asked by some fellow exiles if he could breed a more domestic fox that they could keep as pets. So, he began selectively breeding the most docile foxes. And something strange happened; their coats began to change colors and their ears began taking different shapes.

I wonder why most birds are not as smart as we are ? (thinking of the crow and parrot)

g2w

There is an interesting poster in the window of a local Native American art shop here that say something like: Other cultures are not failed attempts at being like you.

This could also be said for birds.After all, they survive in conditions that would kill us.They never punch a time clock and they don't pay rent.They will never have to worry about our lousy healthcare system.I'm having a hard time figuring out how they are dumber than we are. :)

This could also be said for birds.After all, they survive in conditions that would kill us.They never punch a time clock and they don't pay rent.They will never have to worry about our lousy healthcare system.I'm having a hard time figuring out how they are dumber than we are. :)